Our research is designed to clarify the structure and function of the aortic and other semilunar valves to provide an improved basis for surgical valvuloplasty. According to our view the normal aortic root to which the valve leaflets are attached is a dynamic structure integrated with the leaflets and functioning as a single unit. These studies will continue our current investigations into the structure of aortic valves and compare them with pulmonic and venous valves. The aortic valves are tricuspid and operate under relatively high pressure; the pulmonic and venous valves, respectively tricuspid and bicuspid, operate on relatively low pressures. These functional differences may well be reflected in histological structure. A part of our studies will examine tissue turnover in valves, as an approach to understanding the functional stresses on both normal and diseased valves. Pathological valves available from autopsies will be examined, and efforts will be made surgically to produce models of some pathological states. Our intention in this research is to replace outdated descriptive accounts of the histology of semilunar valves with a functional view of the arrangement of valve tissues. To this end, we will continue the reexamination by light microscopy of the fibrous tissues and cellular constituents of valve walls and leaflets from serial sections of normal and pathological valves, including both diseased and experimentally altered structures. Electron microscopy will be used to clarify surface details of valves and fine structural interrelationships of their tissues. Tissue turnover will be examined with radioisotopic labeling and radioautography, including identification of labeled parts by selective enzymatic digestion of tissues from sections.